#include<bits/stdc++.h>
#include<atcoder/all>
#define rep(i,b) for(int i=0;i<b;i++)
#define rrep(i,b) for(int i=b-1;i>=0;i--)
#define rep1(i,b) for(int i=1;i<b;i++)
#define repx(i,x,b) for(int i=x;i<b;i++)
#define rrepx(i,x,b) for(int i=b-1;i>=x;i--)
#define fore(i,a) for(auto& i:a)
#define rng(x) (x).begin(), (x).end()
#define rrng(x) (x).rbegin(), (x).rend()
#define sz(x) ((int)(x).size())
#define pb push_back
#define fi first
#define se second
#define pcnt __builtin_popcountll

using namespace std;
using namespace atcoder;

using ll = long long;
using ld = long double;
template<typename T> using mpq = priority_queue<T, vector<T>, greater<T>>;
template<typename T> bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<typename T> bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
template<typename T> ll sumv(const vector<T>&a){ll res(0);for(auto&&x:a)res+=x;return res;}
bool yn(bool a) { if(a) {cout << "Yes" << endl; return true;} else {cout << "No" << endl; return false;}}
#define retval(x) {cout << #x << endl; return;}
#define cout2(x,y) cout << x << " " << y << endl;
#define coutp(p) cout << p.fi << " " << p.se << endl;
#define out cout << ans << endl;
#define outd cout << fixed << setprecision(20) << ans << endl;
#define outm cout << ans.val() << endl;
#define outv fore(yans , ans) cout << yans << "\n";
#define outdv fore(yans , ans) cout << yans.val() << "\n";
#define coutv(v) {fore(vy , v) {cout << vy << " ";} cout << endl;}
#define coutv2(v) fore(vy , v) cout << vy << "\n";
#define coutvm(v) {fore(vy , v) {cout << vy.val() << " ";} cout << endl;}
#define coutvm2(v) fore(vy , v) cout << vy.val() << "\n";
using pll = pair<ll,ll>;using pil = pair<int,ll>;using pli = pair<ll,int>;using pii = pair<int,int>;using pdd = pair<ld,ld>;
using vi = vector<int>;using vd = vector<ld>;using vl = vector<ll>;using vs = vector<string>;using vb = vector<bool>;
using vpii = vector<pii>;using vpli = vector<pli>;using vpll = vector<pll>;using vpil = vector<pil>;
using vvi = vector<vector<int>>;using vvl = vector<vector<ll>>;using vvs = vector<vector<string>>;using vvb = vector<vector<bool>>;
using vvpii = vector<vector<pii>>;using vvpli = vector<vector<pli>>;using vvpll = vector<vpll>;using vvpil = vector<vpil>;
using mint = modint998244353;
//using mint = modint1000000007;
//using mint = dynamic_modint<0>;
using vm = vector<mint>;
using vvm = vector<vector<mint>>;
vector<int> dx={1,0,-1,0,1,1,-1,-1},dy={0,1,0,-1,1,-1,1,-1};
ll gcd(ll a, ll b) { return a?gcd(b%a,a):b;}
ll lcm(ll a, ll b) { return a/gcd(a,b)*b;}
#define yes {cout <<"Yes"<<endl;}
#define no {cout <<"No"<<endl;}
const double eps = 1e-10;
const ll LINF = 1001002003004005006ll;
const int INF = 1001001001;
#ifdef MY_LOCAL_DEBUG
#define show(x) cerr<<#x<<" = "<<x<<endl
#define showp(p) cerr<<#p<<" = "<<p.fi<<" : "<<p.se<<endl
#define show2(x,y) cerr<<#x<<" = "<<x<<" : "<<#y<<" = "<<y<<endl
#define show3(x,y,z) cerr<<#x<<" = "<<x<<" : "<<#y<<" = "<<y<<" : "<<#z<<" = "<<z<<endl
#define show4(x,y,z,x2) cerr<<#x<<" = "<<x<<" : "<<#y<<" = "<<y<<" : "<<#z<<" = "<<z<<" : "<<#x2<<" = "<<x2<<endl
#define test(x) cout << "test" << x << endl
#define showv(v) {fore(vy , v) {cout << vy << " ";} cout << endl;}
#define showv2(v) fore(vy , v) cout << vy << "\n";
#define showvm(v) {fore(vy , v) {cout << vy.val() << " ";} cout << endl;}
#define showvm2(v) fore(vy , v) cout << vy.val() << "\n";
#else
#define show(x)
#define showp(p)
#define show2(x,y)
#define show3(x,y,z)
#define show4(x,y,z,x2)
#define test(x)
#define showv(v)
#define showv2(v)
#define showvm(v)
#define showvm2(v)
#endif

struct edge{
    int from,to;
    ll cost;

    edge(int from_=0,int to_=0,ll cost_=0) : from(from_),to(to_),cost(cost_) {}
    bool operator<(const edge& ot){
        return cost < ot.cost;
    }
};

void solve(){
    int h,w; cin>>h>>w;
    vs s(h);
    rep(i,h) cin>>s[i];

    auto isBlock = [&](int i,int j)->bool{
        bool ret = true;
        rep(ii,3) rep(jj,3){
            int x = i+ii;
            int y = j+jj;
            if (x<0||x>=h||y<0||y>=w||s[x][y]=='#') ret = false;
        }
        return !ret;
    };

    auto isReachable = [&]()->bool{
        vector<vector<edge>> e(h*w);
        rep(i,h) rep(j,w){
            if (isBlock(i,j)) continue;
            rep(kk,8){
                int x,y;
                x = i + dx[kk];
                y = j + dy[kk];
                if (x <= h-1 && x >= 0 && y <= w-1 && y >= 0 && !isBlock(x,y)){
                    int from = i*w + j;
                    int to = x*w + y;
                    e[from].pb(edge(from,to,0));
                }
            }
        }

        vl dist(h*w,LINF);
        mpq<pli> q;
        
        int st = 0;
        dist[st] = 0;
        q.push({dist[st] , st});
        
        while(!q.empty()){
            pli p = q.top();
            q.pop();
            ll nowDist = p.first;
            int from = p.second;
        
            if (dist[from] < nowDist) continue;
        
            fore(ey , e[from]){
                int to = ey.to;
                ll cost = ey.cost;
        
                if (chmin(dist[to] , nowDist + cost)){
                    q.push({dist[to] , to});
                }
            }
        }
        int go = (h-3)*w + (w-3);
        return (dist[go]!=LINF);
    };

    int ans = 2;
    if (!isReachable()) ans = 0;
    else{
        rep(i,h) rep(j,w){
            if (i<3&&j<3) continue;
            if (i>=h-3&&j>=w-3) continue;
            if (s[i][j] == '#') continue;
            s[i][j] = '#';
            if (!isReachable()) ans = 1;
            s[i][j] = '.';
        }
    }
    out;

    return;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);

    int t = 1;
    //cin>>t;

    rep(i,t){
        solve();
    }

    return 0;
}